Execute and profile the following script:

<?php
class Test implements ArrayAccess {
private $container = array();

public function offsetSet($offset, $value) {
    $this->container[$offset] = $value;
}
public function offsetExists($offset) {
    return isset($this->container[$offset]);
}
public function offsetUnset($offset) {
    unset($this->container[$offset]);
}
public function offsetGet($offset) {
    return isset($this->container[$offset]) ? $this->container[$offset] : null;
}

}

$test = new Test();
$test['test'] = 'test';
echo $test['test'];
?>